Branch death, or flagging, at multiple locations in the crown of a diseased elm.

Dutch elm disease is a fungal disease of elm trees which is spread by the elm bark beetle. Although believed to be originally native to Asia, it has been accidentally introduced into America and Europe, where it has devastated native populations of elms which had not had the opportunity to evolve resistance to the disease. The name Dutch elm disease refers to the identification of the disease in the 1920s in the Netherlands; the disease is not specific to the Dutch Elm hybrid. Scientific classification redirects here. ... For the fictional character, see Fungus the Bogeyman. ... Subphyla/Classes Archaeascomycetes Euascomycetes Hemiascomycetes or Pezizomycotina Laboulbeniomycetes Eurotiomycetes Lecanoromycetes Leotiomycetes Pezizomycetes Sordariomycetes Dothideomycetes (and many more) Saccharomycotina Saccharomycetes Taphrinomycotina Neolectomycetes Pneumocystidomycetes Schizosaccharomycetes Taphrinomycetes The Ascomycota, formerly known as the Ascomycetae, or Ascomycetes, are a Division of Fungi, whose members are commonly known as the Sac Fungi, which produce spores... Classes Arthoniomycetes Chaetothyriomycetes Dothideomycetes Eurotiomycetes Laboulbeniomycetes Lecanoromycetes Leotiomycetes Orbiliomycetes Pezizomycetes Sordariomycetes mitosporic Pezizomycotina Pezizomycotina is a subphylum of the Ascomycota and was previously called the Euascomycota. ... Orders Diaporthales Hypocreales Microascales Sordariales Sordariomycetes is a class of the subdivision, Pezizomycotina, which includes ascomycetous fungi. ... Image File history File links Dutchelmdisease. ... Image File history File links Dutchelmdisease. ... For the fictional character, see Fungus the Bogeyman. ... Species See Elm species, varieties, cultivars and hybrids Elms are deciduous and semi-deciduous trees making up the genus Ulmus, family Ulmaceae, found throughout the Northern Hemisphere from Siberia to Indonesia, Mexico to Japan. ... Genera See text. ... Dutch Elm Major is a cultivar derived from a crossing of Wych Elm with Field Elm . ...

Overview

The causative agents of Dutch Elm Disease are ascomycete microfungi. Three species are now recognized, Ophiostoma ulmi, which afflicted Europe in 1910, reaching North America on imported timber in 1928, Ophiostoma himal-ulmi, a species endemic to the western Himalaya. A third, extremely virulent species, Ophiostoma novo-ulmi, was first described in Europe and North America in the 1940s and has devastated elms in both areas since the late 1960s (Spooner & Roberts, 2005). The origin of O. novo-ulmi remains unknown (Spooner & Roberts, 2005), but may have arisen as a hybrid between O. ulmi and O. himal-ulmi ^[1] The new species was widely believed to have originated in China, but a comprehensive survey there in 1986 found no trace of it, although elm bark beetles were very common ^[1]. Classes Archaeascomycetes Hemiascomycetes Euascomycetes Neolectomycetes Pezizomycotina Pneumocystidomycetes Saccharomycotina Schizosaccharomycetes Taphrinomycetes mitosporic Ascomycota Members of the Division Ascomycota are known as the Sac Fungi and are fungi that produce spores in a distinctive type of microscopic sporangium called an ascus (Greek for a bag or wineskin). This monophyletic grouping was formerly... Microfungi are organisms such as mold and mildew as well as rust, which cause plant diseases. ... Perspective view of the Himalaya and Mount Everest as seen from space looking south-south-east from over the Tibetan Plateau. ... Genera See text. ...

The disease is spread by two species of bark beetles (Family: Curculionidae, Subfamily: Scolytinae): the native elm bark beetle, Hylurgopinus rufipes , and the European elm bark beetle, Scolytus multistriatus. Both act as vectors for infection. In an attempt to block the fungus from spreading further, the tree reacts to the presence of the fungus by plugging its own xylem tissue with gum and tyloses, bladder-like extensions of the xylem cell wall. As the xylem (one of the two types of vascular tissue produced by the vascular cambium, the other being the phloem) delivers water and nutrients to the rest of the plant, these plugs prevent them from travelling up the trunk of the tree, eventually killing it. The first symptom of infection is usually an upper branch of the tree with leaves starting to wither and yellow in summer, months before the normal autumnal leaf shedding. This progressively spreads to the rest of the tree, with further dieback of branches. Eventually, the roots die, starved of nutrients from the leaves. Subgroups See Subgroups of Curculionidae. ... In epidemiology, a vector is an organism that does not cause disease itself but which spreads infection by conveying pathogens from one host to another. ... In vascular plants, xylem is one of the two types of transport tissue, phloem being the other one. ... Plant cells separated by transparent cell walls. ... Cross section of celery stalk, showing vascular bundles, which include both phloem and xylem. ... The vascular cambium is a lateral meristem: The vascular cambium is the source of both the secondary xylem (inwards) and the secondary phloem (outwards), and hence is located between these tissues in the stem. ... In vascular plants, phloem is the living tissue that carries organic nutrients, particularly sucrose, a sugar, to all parts of the plant where needed. ... The coniferous Coast Redwood, the tallest tree species on earth. ...

Often, not all the roots die: the roots may put up small suckers. These may grow up for some years into small elm trees, but after a decade or so the new trunks become large enough to support the bark beetles, and with their inevitable arrival the fungus returns, and the new tree dies.

Disease range

Europe

Dutch elm disease was first noticed in Europe in 1910, and spread slowly, reaching Britain in 1927. This first strain was a relatively mild one, which only killed a small proportion of elms, more often just killing scattered branches, and had largely died out by 1940. It was isolated in Holland in 1921 by Marie Beatrice Schwarz, a pioneering Dutch phytopathologist, and this discovery would lend the disease its name.[1]

In about 1967, a new, far more virulent strain arrived in Britain on a shipment of Rock Elm logs from North America, and this strain proved both highly contagious and lethal to all of the European native elms; more than 25 million trees died in the UK alone. By 1990-2000, very few mature elms were left in Britain or much of northern Europe. One of the most distinctive English countryside trees, the English Elm U. procera Salisb. (see e.g. John Constable's painting The Hay Wain), is particularly susceptible. Thirty years after the epidemic, these magnificent trees, which often grew to > 45 m high, are long gone. The species still survives in hedgerows, as the roots are not killed and send up root sprouts ("suckers"). These suckers rarely reach more than 5 m tall before succumbing to a new attack of the fungus. However, established hedges kept low by clipping have remained apparently healthy throughout the nearly 40 years since the onset of the disease in the UK. Binomial name Ulmus thomasii Sarg. ... For other uses, see England (disambiguation). ... Binomial name Ulmus minor var. ... A self portrait by John Constable John Constable (11 June 1776 – 31 March 1837) was an English Romantic painter. ... The Hay Wain is an oil on canvas painting by John Constable. ... For other meanings, see hedge. ...

Sign on A27 road, Brighton, UK

The largest concentration of mature elm trees remaining in England is in Brighton & Hove, East Sussex, where 15,000 elms still stand (2005 figures), several of which are estimated to be over 400 years old. Their survival is owing to the isolation of the area, between the English Channel and the South Downs, and the assiduous efforts of local authorities to identify and remove infected sections of trees immediately they show signs of the disease. Empowered by the Dutch Elm Disease (Restriction on Movement of Elms) (Amendment) Order 1988 [2], local authorities may order the destruction of any infected trees or timber, although in practice they usually do it themselves, successfully reducing the numbers of elm bark beetle Scolytus spp, the vector of Elm Disease.[3] Brighton & Hove (or Brighton and Hove) is a unitary authority area and city on the south coast of England. ... East Sussex is a county in South East England. ... For the Thoroughbred racehorse of the same name, see English Channel (horse). ... Near Beachy Head The South Downs is one of the two areas of chalk downland in southern England. ...

United States

Certified arborist removing infected elm in Saint Paul, Minnesota.

The disease was first reported in the United States in 1928, with the beetles believed to have arrived in a shipment of logs from the Netherlands destined for the Ohio furniture industry. The disease spread slowly from New England westward and southward, almost completely destroying the famous Elms in the 'Elm City' of New Haven, reaching the Detroit area in 1950[4], the Chicago area by 1960, and Minneapolis by 1970. For an overview of the Twin Cities metropolitan area, see Minneapolis-Saint Paul. ... This article is about the U.S. State. ... For the UK band, see Furniture (band). ... This article is about the region in the United States of America. ... This article is about the city in Connecticut. ... Detroit redirects here. ... Flag Seal Nickname: The Windy City Motto: Urbs In Horto (Latin: City in a Garden), I Will Location Location in Chicagoland and northern Illinois Coordinates , Government Country State Counties United States Illinois Cook, DuPage Mayor Richard M. Daley (D) Geographical characteristics Area     City 606. ... Minneapolis redirects here. ...

Canada

Dutch elm disease reached Eastern Canada during the Second World War, and spread to Ontario in 1967, Manitoba in 1975 and Saskatchewan in 1981. The largest white elm known to exist in Ontario, the Sauble Elm, succumbed to the disease and was cut down in September of 1968 (see External Link). In Toronto, Ontario, as much as 80% of the elm trees have been lost to Dutch elm disease, and many more have fallen victim to the disease in Ottawa and Montreal and other cities during the 1970s and 1980s. Alberta and British Columbia are the only provinces that are currently free of Dutch elm disease, although an elm tree in southeastern Alberta was found diseased in 1998 and was immediately destroyed before the disease could spread any further. Thus, this was an isolated case. Today, Alberta has the largest number of elms unaffected by Dutch elm disease in the world. Aggressive measures are being taken to prevent the spread of the disease into Alberta as well as further progression of the disease in other parts of Canada. The City of Edmonton has banned elm pruning from March 31 to October 1, since fresh pruning wounds will attract the beetles during the warmer months. This article is about the Canadian province. ... Motto: Gloriosus et Liber (Latin: Glorious and free) Capital Winnipeg Largest city Winnipeg Official languages English French (de facto) Government Lieutenant-Governor John Harvard Premier Gary Doer (NDP) Federal representation in Canadian Parliament House seats 14 Senate seats 6 Confederation July 15, 1870 (5th) Area  Ranked 8th Total 647,797... For other uses, see Saskatchewan (disambiguation). ... Template:Hide = Motto: Template:Unhide = Diversity Our Strength Image:Toronto, Ontario Location. ... For other uses, see Alberta (disambiguation). ... Motto: Splendor sine occasu (Latin: Splendour without diminishment) Capital Victoria Largest city Vancouver Official languages English (de facto) Government Lieutenant-Governor Steven Point Premier Gordon Campbell (BC Liberal) Federal representation in Canadian Parliament House seats 36 Senate seats 6 Confederation July 20, 1871 (6th province) Area  Ranked 5th Total 944... For other uses, see Alberta (disambiguation). ... For other uses, see Alberta (disambiguation). ... This article is about the city in Alberta, Canada. ...

Practical Information for the Elm tree owner: The disease is caused by a fungus. It is primarily spread 3 ways: 1) by beetle vectors which carry the fungus from tree to tree (the beetle doesn't kill the tree, the fungus it carries does). 2) through direct contact of an infected tree's roots with a neighboring healthy tree. 3) by pruning of a healthy tree with saws which have been used to take down diseased trees. This third method of spread is common and not recognized by many tree pruning and removal services. Arborists at Kansas State University claim that cleaning blades with a 10% solution of a household bleach will prevent this type of spread. Owners of healthy trees should be vigilant about the companies they hire to prune healthy trees. Be certain blades are disinfected between use to remove dead trees and use to prune healthy trees. For the fictional character, see Fungus the Bogeyman. ... In epidemiology, a vector is an organism that does not cause disease itself but which spreads infection by conveying pathogens from one host to another. ...

Treatment

The first fungicide used for preventive treatment of Dutch elm disease was Lignasan BLP (carbendazim phosphate), which was introduced in the 1970s. This had to be injected into the base of the tree using specialized equipment, and was never especially effective. It is still sold under the name "Elm Fungicide". Arbotect (thiabendazole hypophosphite) became available some years later, and it has been proven effective. Arbotect must be injected every 2 to 3 years to provide ongoing control; the disease generally cannot be eradicated once a tree is infected. Status: ISO 1750 (published) IUPAC: methyl benzimidazol-2-ylcarbamate Formula: C9H9N3O2 Activity: fungicides (benzimidazole fungicides; benzimidazolylcarbamate fungicides) Categories: | ... Thiabendazole is a fungicide and parasiticide used primarily to control mold, blight, and other fungally caused diseases in fruits and vegetables. ...

Alamo (propiconazole) has become available more recently and shows some promise, though several university studies show it to be less effective than Arbotect treatments. Alamo is primarily recommended for treatment of Oak Wilt. Binomial name Ceratocystis fagacearum (T. W. Bretz) J. Hunt Oak wilt is a fungal disease which can quickly kill an oak tree. ...

Treatment of diseased trees is costly and at best will prolong the life of the tree, perhaps by as many as five or ten years. It is usually only justified when a tree has unusual symbolic value or occupies a particularly important place in the landscape.

Resistant trees

Research to select resistant cultivars and varieties began in the Netherlands in 1928, and in the USA since the disease became endemic there. Initial efforts in the Netherlands involved crossing varieties of U. minor and U. glabra, but later included the Himalayan or Kashmir Elm U. wallichiana as a source of anti-fungal genes. Early efforts in the USA involved the hybridization of the Chinese Elm with the American Elm, and produced a resistant tree, but that lacked the beauty, traditional shape, and landscape value of the American Elm. Few were planted.

Cultivars

Three major groups of resistant American Elm cultivars are commercially available:

• The Princeton Elm, a cultivar selected in 1922 by Princeton Nurseries for its landscape merit. By happy coincidence, this cultivar was revealed to be highly resistant in inoculation studies carried out by the USDA in the early 1990s. Because mature trees planted in the 1920s still remain, the properties of the mature plant are well known.
• The Liberty Elm, a set of five cultivars produced through selection over several generations starting in the 1970s. Marketed as a single variety, nurseries selling the "Liberty Elm" actually distribute the five cultivars at random. Two of the cultivars are covered by patents.
• The Valley Forge elm, and some related cultivars, have demonstrated resistance to Dutch elm disease, approximately equal to that of the Princeton Elm cultivar, in controlled USDA tests.

In 2007, the Elm Recovery Project from the University of Guelph in Ontario, Canada reported that cuttings from healthy surviving old elms surveyed across Ontario had been grown to produce a bank of resistant trees, isolated for selective breeding of highly resistant cultivars [5] . Year 1922 (MCMXXII) was a common year starting on Sunday (link will display full calendar) of the Gregorian calendar. ...

The Slippery or Red Elm U. rubra, that overlaps the range of the American Elm, is less susceptible to Dutch elm disease than many elms, but this quality seems to have somehow largely evaded the attention of the resistance programme. Binomial name Ulmus rubra Muhl. ...

Even resistant cultivars can become infected, particularly if the tree is under stress from drought and other environmental conditions, and if the disease pressure is high. With the exception of the Princeton Elm, no trees have yet been grown to maturity. The oldest Liberty Elm was planted in about 1980, and the trees cannot be said to be mature until they have reached an age of sixty years.

In 2001, English Elm U. procera was genetically engineered to resist disease, in experiments at Abertay University, Dundee, Scotland, by transferring anti-fungal genes into the elm genome using minute DNA-coated ball bearings [6]. However, there are no plans to release the trees into the countryside. Binomial name Ulmus minor var. ... For other uses, see Dundee (disambiguation). ... This article is about the country. ...

Hybrid cultivars

There have been many attempts to breed disease resistant cultivar hybrids and they have usually involved a genetic contribution from Asian elm species which have demonstrable resistance to this fungal disease. Much of the early work in Europe was undertaken in the Netherlands. The Dutch research programme ended after 64 years in 1992. The programme had two major successes: 'Columella' and 'Nanguen' (Lutèce), both found to be actually immune to the disease when inoculated with unnaturally high doses of the fungus. The patent for the Lutèce clone was purchased by the French Institut National de la Recherche Agronomique (INRA), which subjected the tree to 20 years of field trials in the Bois de Vincennes, Paris, before releasing it for sale in 2002. Year 1992 (MCMXCII) was a leap year starting on Wednesday (link will display full 1992 Gregorian calendar). ... The lake Hippodrome de Vincennes The Bois de Vincennes is a park in the English landscape manner to the east of Paris. ... This article is about the capital of France. ... Also see: 2002 (number). ...

In Italy, research is continuing at the Istituto per la Protezione delle Piante, Florence, to produce a wide range of disease-resistant trees using a variety of Asiatic species crossed with the early Dutch hybrid Plantyn (elm hybrid) as a safeguard against any future mutation of the disease. Four trees with very high levels of resistance; 'San Zanobi' and 'Plinio', were released in 2003, followed four years later by 'Arno' and 'Fiorente'. All four feature the Siberian Elm Ulmus pumila as a source of disease-resistance genes. Plantyn (Anglicized form of Plantijn) was one of three Dutch hybrid elms released in 1973, but was to prove no more resistant to Dutch elm disease than its contemporaries Dodoens and Lobel. ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... Binomial name Ulmus pumila L. Siberian Elm (Ulmus pumila), is a small to medium-sized tree found in Turkestan to eastern Siberia, northern China, and in the United States. ...

The European White Elm

There is also the unique example of the European White Elm U. laevis that has little innate resistance to Dutch elm disease but is eschewed by the vector bark beetles and only rarely becomes infected. Research published in the Canadian Journal of Forest Research has indicated that it is the presence of certain organic compounds, such as triterpenes and sterols, that serves to make the tree bark unattractive to the beetle species that spread the disease. Binomial name Pall. ... Many terpenes are derived from conifer resins, here a pine. ... Sterols are a subgroup of steroids with a hydroxyl group in the 3-position of the A-ring. ...

Possible earlier occurrences

A less devastating form of the disease, caused by a different fungus, had possibly been present in Britain for some time, as this passage in Richard Jefferies' 1883 book, Nature near London, shows: John Richard Jefferies John Richard Jefferies (November 6, 1848 - August 14, 1887 ) was an English nature writer, essayist and journalist. ...

There is something wrong with elm trees. In the early part of this summer, not long after the leaves were fairly out upon them, here and there a branch appeared as if it had been touched with red-hot iron and burnt up, all the leaves withered and browned on the boughs. First one tree was thus affected, then another, then a third, till, looking round the fields, it seemed as if every fourth or fifth tree had thus been burnt. [...] Upon mentioning this I found that it had been noticed in elm avenues and groups a hundred miles distant, so that it is not a local circumstance.

This suggestion remains largely speculative, and there is no proof that it was caused by a fungus related to Dutch elm disease.

From analysis of pollen in peat samples, it is apparent the elm all but disappeared from Europe during the mid-Holocene period about 6000 years ago. Examination of sub-fossil elm wood has suggested that Dutch elm disease may have been responsible [7].

References

• Forestry Commission. Dutch elm disease in Britain [8], UK.
• Institut National de la Recherche Agronomique. Lutèce, a resistant variety brings elms back to Paris [9], Paris, France.
• Macmillan Science Library: Plant Sciences. Dutch Elm Disease. [10],
• Martín-Benito D., Concepción García-Vallejo M., Alberto Pajares J., López D. 2005. Triterpenes in elms in Spain. Can. J. For. Res. 35: 199–205 (2005). [11]
• Santini A., Fagnani A., Ferrini F. & Mittempergher L., (2002) San Zanobi and Plinio elm trees. HortScience 37(7): 1139-1141. 2002. American Society for Horticultural Science, Alexandria, VA 22314, USA.
• Santini A., Fagnani A., Ferrini F., Mittempergher L., Brunetti M., Crivellaro A., Macchioni N., Elm breeding for DED resistance, the Italian clones and their wood properties. Invest Agrar: Sist Recur For (2004) 13 (1), 179-184. 2004. [12]
• Spooner B. and Roberts P. 2005. Fungi. Collins New Naturalist series No. 96. HarperCollins Publishers, London.

External links

• The Sauble Elm (Ontario, Canada)
• Elm Recovery Project - Guelph University (Canada)
• Dutch elm disease - info from the Government of Alberta
• Dutch elm disease - info from the Government of British Columbia
• DED info from Rainbow Treecare Scientific Advancements
• The Mid-Holocene Ulmus decline: a new way to evaluate the pathogen hypothesis